The birth of Buddhism begins with the birth of Siddhartha Gautama, who would one day become known as Buddha ("the enlightened one"). Siddhartha was the son of a wealthy warrior-king . A holy man told Siddhartha's father that if Siddhartha ever ventured outside the palace it would bring an end to his kingdom.
Out of fear, Siddhartha's father sheltered him in a palace with anything a human could ever desire. When Siddhartha reached the age of 20, he became bored with the all the of wealth in his possession and speculated that there is more to life that money and servants. Siddhartha plotted to leave the palace to discover the outside world.
On Siddhartha's first time out of the palace, he encountered an old man suffering. Siddhartha was frightened, and learned for the first time that humans grow old. He returned to the palace, fearful of his discovery.
Questions and curiosity led Siddhartha to take more journeys of exploration, and on one of these trips he encountered a diseased man who was suffering from his sickness. Siddhartha learned that humans become ill and suffer.
On his next journey, Siddhartha encountered a corpse. Siddhartha learned that life is temporary and people die.